The subject matter disclosed herein relates generally to energy management of hydrocarbon fueled residential hot water heaters, and more particularly to monitoring household usage of hot water heated by such water heaters.
Basic hot water heaters generally include a hot water reservoir, such as a thermally insulated hot water tank, a heating element such as a gas burner, and a thermostat that controls the burner to maintain a set temperature of the water in the reservoir. In general, the temperature of the water is maintained at a relatively constant level corresponding to a set point of the thermostat, for example 140 degrees Fahrenheit (F.), until it is needed. As hot water is dispensed from the reservoir, cold water is admitted thereby lowering the bulk temperature of the water. The temperature of the water in the reservoir may also be lowered as a result of heat loss through the walls of the reservoir. When the water temperature drops below the set point of the thermostat, the heating element is activated to restore the temperature of the water to the setpoint temperature.
The advent of home energy management (HEM) systems has created an increasing homeowner interest in total energy consumption in the home. A large portion of residential natural gas usage is to heat water in addition to heating the residence. Being able to accurately ascertain how much hot water is being consumed over a specific timeframe along with the associated cost would be advantageous for a home energy management system, especially when coupled with the ability to determine the amount of this usage without having to hire a plumber to install (or manually install) a hot water flowmeter.